The present invention relates to a process for casting a metal alloy continuously in a semi-liquid state, in particular for casting a light alloy usable for casting components of the fuel supply system of a heat engine. The invention further relates to a furnace for performing this process.
A static mixer is known from Italian Pat. No. 1,119,287 filed Jun. 20, 1979 and entitled: "Process for the preparation of a mixture comprising a solid phase and a liquid phase of a metal alloy and device for performing this process", the static mixer being of the type formed by a cylindrical casting channel within which are disposed in succession a series of helically wound blades or paddles, by means of which it is possible to cast a metal alloy by obtaining partial solidification, during casting, within the passage of the static mixer, with simultaneous mixing of the solid phase, upon formation, with the remaining liquid phase in such a way as to form at the output from the static mixer a solid/liquid mixture in which the solid phase separating out from the liquid alloy is uniformly dispersed in suspension within the liquid alloy itself. The mixture thus obtained is stable for a sufficiently long period of time to permit collection in a ladle and subsequent casting in moulds to obtain castings having particular and valuable microstructural characteristics.
To be able to obtain these characteristics, however, the solid/liquid mixture must be obtained in stationary fluid dynamics conditions and it is necessary to be able to control with precision and speed the physical and dynamic parameters of the casting (temperature gradient of cooling of the alloy, speed of transit through the static mixer, etc); this necessity involves, on the one hand, having to effect casting by the use of pressurised furnaces so that the casting cannot be performed continuously, but only as a batch process; and on the other hand it involves the necessity of rejecting not inconsiderable quantities of alloy and, above all, of having to dismantle and clean the static mixer in the interval between one casting and the next; bearing in mind that the furnaces cannot, for practical reasons, have a very high capacity (for example greater than 1000 Kg) this latter disadvantage involves high maintenance costs and, finally, a high cost per unit of cast alloy and a low overall productivity of the system.